Possible Clues:

• Hard to bear
• Case of pneumonia's almost entirely miserable
• Agonising facts cut into me
• Harrowing tub farmers' union's invested in
• Sore, perhaps
• “While pensive poets ____ vigils keep, / Sleepless themselves to give their readers sleep” (Alexander Pope)
• Bucketful of perverse fun, thus for the masochist?
• Like some dental work
• Tender Christian missionary recruiting in force
• Agonizing